Biodegradable composite yarn structure and method

ABSTRACT

The techniques of this disclosure generally relate to prosthesis formed from a biodegradable composite yarn. The biodegradable composite yarn includes a permanent core and a biodegradable shell. The biodegradable shell slowly dissolves over a period of time when placed in a vessel. As the biodegradable shell dissolves, openings are created in the prosthesis that are filled with tissue from the vessel wall of the vessel. The integration of the tissue into the prosthesis provides biological fixation of prosthesis in the vessel and prevents endoleaks and migration of prosthesis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/591,601, filed on Nov. 28, 2017, entitled “ADVANCED GRAFT MATERIALS FOR ENDOVASCULAR APPLICATIONS” of Borglin et al., which is incorporated herein by reference in its entirety.

FIELD

The present technology is generally related to an intra-vascular device and method. More particularly, the present application relates to a device for treatment of intra-vascular diseases.

BACKGROUND

A conventional stent-graft typically includes a radially expandable reinforcement structure, formed from a plurality of annular stent rings, and a cylindrically shaped layer of graft material defining a lumen to which the stent rings are coupled. Stent-grafts are well known for use in tubular shaped human vessels.

To illustrate, endovascular aneurysmal exclusion is a method of using a stent-graft to exclude pressurized fluid flow from the interior of an aneurysm, thereby reducing the risk of rupture of the aneurysm and the associated invasive surgical intervention.

The graft material of traditional stent-grafts is extremely hydrophobic and presents a hostile environment for the recruitment and proliferation of cells. The inability of tissue to integrate into the graft material prevents the biological fixation of the stent-graft in vessels and makes the stent-graft susceptible to endoleaks and migration.

SUMMARY

The techniques of this disclosure generally relate to prosthesis formed from a biodegradable composite yarn. The biodegradable composite yarn includes a permanent core and a biodegradable shell. The biodegradable shell slowly dissolves over a period of time when placed in a vessel. As the biodegradable shell dissolves, openings are created in the prosthesis that are filled with tissue from the vessel wall of the vessel. The integration of the tissue into the prosthesis provides biological fixation of prosthesis in the vessel and prevents endoleaks and migration of prosthesis.

In one aspect, the present disclosure provides a prosthesis having a biodegradable composite yarn including a permanent core and a biodegradable shell.

In another aspect, the disclosure provides an assembly including a vessel having a vessel wall and a prosthesis in contact with the vessel wall. The prosthesis includes a permanent core and a biodegradable shell.

In yet another aspect, the disclosure provides a method including forming a biodegradable composite yarn having a permanent core and a biodegradable shell. The biodegradable composite yarn is combined to form a prosthesis having a biodegradable composite graft material.

The details of one or more aspects of the disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the techniques described in this disclosure will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a biodegradable composite yarn stent-graft in accordance with one embodiment.

FIG. 2 is a cross-sectional view of a biodegradable composite yarn used to fabricate the stent-graft of FIG. 1 in accordance with one embodiment.

FIG. 3 is a plan view of the biodegradable composite yarn of FIG. 2 in accordance with one embodiment.

FIG. 4 is an enlarged plan view of the region IV of the stent-graft of FIG. 1 in accordance with one embodiment.

FIG. 5 is a cross-sectional view of the graft material along the line V-V of FIG. 4 in accordance with one embodiment.

FIG. 6 is an enlarged plan view of a section of the graft material including two horizontal biodegradable composite yarns interlaced with two vertical biodegradable composite yarns prior to dissolution of the biodegradable shells in accordance with one embodiment.

FIG. 7 is a cross-sectional view of the graft material along the line VII-VII of FIG. 6 upon initial deployment on a vessel wall in accordance with one embodiment.

FIG. 8 is an enlarged plan view of the section of the graft material of FIG. 6 after dissolution of the biodegradable shells in accordance with one embodiment.

FIG. 9 is a cross-sectional view of the graft material along the line IX-IX of FIG. 8 after a period of time after deployment on the vessel wall in accordance with one embodiment.

FIG. 10 is a cross-sectional view of a vessel assembly including the stent-graft of FIG. 1 after initial deployment within a vessel having a dissection in accordance with one embodiment.

FIG. 11 is an enlarged cross-sectional view of a region XI of the vessel assembly of FIG. 10.

FIG. 12 is a cross-sectional view of the region XI of the vessel assembly of FIG. 10 after a period of time after deployment of the stent-graft within the vessel in accordance with one embodiment.

FIG. 13 is a cross-sectional view of a vessel assembly including a stent-graft in accordance with one embodiment.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of a biodegradable composite yarn stent-graft 100 in accordance with one embodiment. Referring now to FIG. 1, stent-graft 100, sometimes called a prosthesis, includes a biodegradable composite yarn graft material 102 and one or more stent rings 104 coupled to graft material 102. Illustratively, stent rings 104 are self-expanding stent rings, e.g., nickel titanium alloy (NiTi), sometimes called Nitinol, or self-expanding members. The inclusion of stent rings 104 is optional and in one embodiment stent rings 104 are not included. In another embodiment, stent rings 104 are balloon expandable stents.

In accordance with this embodiment, graft material 102 includes a proximal opening 106 at a proximal end 108 of graft material 102 and a distal opening 110 at a distal end 112 of graft material 102.

Further, stent-graft 100 includes a longitudinal axis L. A lumen 114 is defined by graft material 102, and generally by stent-graft 100. Lumen 114 extends generally parallel to longitudinal axis L and between proximal opening 106 and distal opening 110 of stent-graft 100.

As used herein, the proximal end of a prosthesis such as stent-graft 100 is the end closest to the heart via the path of blood flow whereas the distal end is the end furthest away from the heart during deployment. In contrast and of note, the distal end of the catheter is usually identified to the end that is farthest from the operator/handle while the proximal end of the catheter is the end nearest the operator/handle.

For purposes of clarity of discussion, as used herein, the distal end of the catheter is the end that is farthest from the operator (the end furthest from the handle) while the distal end of stent-graft 100 is the end nearest the operator (the end nearest the handle), i.e., the distal end of the catheter and the proximal end of stent-graft 100 are the ends furthest from the handle while the proximal end of the catheter and the distal end of stent-graft 100 are the ends nearest the handle. However, those of skill in the art will understand that depending upon the access location, stent-graft 100 and the delivery system descriptions may be consistent or opposite in actual usage.

Graft material 102 is cylindrical having a substantially uniform diameter. However, in other embodiments, graft material 102 varies in diameter, is bifurcated at distal end 112, and/or is a multi-limbed device for branching applications. Graft material 102 includes an inner surface 116 and an opposite outer surface 118, e.g., cylindrical surfaces in accordance with this embodiment.

Graft material 102 includes biodegradable composite yarns which are woven, knitted, sewn, or otherwise combined to create graft material 102. In one embodiment, yarns are long string like members, sometimes called threads, fibers, or filaments.

FIG. 2 is a cross-sectional view of a biodegradable composite yarn 200 used to fabricate stent-graft 100 of FIG. 1 in accordance with one embodiment. FIG. 3 is a plan view of biodegradable composite yarn 200 of FIG. 2 in accordance with one embodiment.

Referring to FIGS. 2 and 3 together, biodegradable composite yarn 200 includes a permanent core 202 and a biodegradable shell 204. In FIGS. 2 and 3, biodegradable shell 204 as indicated in a dashed line to allow visualization of permanent core 202 for clarity. For example, in the view of FIG. 3, permanent core 202 would be entirely encased within biodegradable shell 204 and would not be visible.

In one embodiment, biodegradable composite yarn 200 is formed by coextruding permanent core 202 and a biodegradable shell 204 at the same time. Permanent core 202 is completely enclosed and encased in biodegradable shell 204.

In one embodiment, permanent core 202 is permanent, e.g., will last in the human body for an extended period of time such as 10 years or more. Permanent core 202 is sometimes called non-absorbable, persistent, or an inner non-absorbable fiber. In one embodiment, permanent core 202 is polyester terephthalate (PET), expanded polyester terephthalate (ePET), or other permanent graft material or textile.

In contrast to permanent core 202, biodegradable shell 204 is a biodegradable material, i.e., is biodegradable. Biodegradable shell 204 is sometimes called an outer biodegradable layer. As used herein, biodegradable means capable of being broken down in the human body, e.g., through contact with fluid such as blood and/or tissue such as a vessel wall. Examples of biodegradable shell 204 include polymer polyglycolic-lactic acid (PLGA), poly(glycerol sebacate) (PGS), Polyglycolic acid (PGA), or Poly Lactic Acid (PLA).

Permanent core 202 provides long term mechanical strength while biodegradable shell 204 provides acute strength and impermeability to prevent endoleaks. As discussed in further detail below, as biodegradable shell 204 degrades, the drop in textile density creates openings, sometimes called ingress channels, through which tissue grows.

In one embodiment, permanent core 202 is a long cylindrical structure, e.g., a string like member, having a diameter D. Permanent core 202 includes a longitudinal axis L1 at a center of permanent core 202. Permanent core 202 includes a cylindrical outer surface 206.

Biodegradable shell 204 is an annular cylinder, sometimes called a hollow cylinder, that surrounds and encases permanent core 202. Biodegradable shell 204 also includes longitudinal axis L1 such that biodegradable shell 204 and permanent core 202 are coaxial. Biodegradable shell 204 includes a cylindrical inner surface 208 and a cylindrical outer surface 210. Cylindrical inner surface 208 is separated from cylindrical outer surface 210 by a thickness T1, sometime called the outer radius of biodegradable shell 204. Cylindrical inner surface 208 of biodegradable shell 204 is directly on cylindrical outer surface 206 of permanent core 202.

FIG. 4 is an enlarged plan view of the region IV of stent-graft 100 of FIG. 1 in accordance with one embodiment. Referring now to FIGS. 1 through 4 together, graft material 102 includes a plurality of biodegradable composite yarns 200. Biodegradable composite yarns 200 are illustrated as including a plurality of vertical biodegradable composite yarns 200V and a plurality of horizontal biodegradable composite yarns 200H interlaced with one another. This arrangement of biodegradable composite yarns 200 is illustrative only and in light of this disclosure those of skill in the art will understand that biodegradable composite yarns 200 can be combined in any one of a number of different fashions to form graft material 102. For example, biodegradable composite yarns 200 are woven, knitted, sewn, or otherwise combined to create graft material 102.

FIG. 5 is a cross-sectional view of graft material 102 along the line V-V of FIG. 4 in accordance with one embodiment. Referring out of FIGS. 4 and 5 together, in accordance with this embodiment, biodegradable shell 204 has a greater elasticity than permanent core 202. This elasticity of biodegradable shell 204 allows a tight interlacing of biodegradable composite yarns 200.

For example, a vertical biodegradable composite yarns 200V contacts a horizontal biodegradable composite yarns 200H as illustrated in FIG. 5. At the point of contact 502, biodegradable shells 204 of each of biodegradable composite yarns 200H, 200V are pressed into one another and deform due to the elasticity of biodegradable shells 204. Accordingly, the un-deformed standard thickness T1 of biodegradable shells 204 is reduced to a lesser thickness T2 at point of contact 502.

Due to this elasticity and deformation of biodegradable shells 204, biodegradable composite yarns 200 are tightly interlaced minimizing the porosity of graft material 102. This, in turn, minimizes and essentially eliminates leaks through graft material 102, e.g., type IV endoleaks.

Over time, biodegradable shells 204 biodegrade and dissolve. This creates/enlarges openings, sometimes called ingress channels, in graft material 102 to encourage tissue integration therein. An example of how the dissolution of biodegradable shells 204 and tissue integration is set forth below in reference to FIGS. 6-9.

FIG. 6 is an enlarged plan view of a section of graft material 102 including two horizontal biodegradable composite yarns 200H interlaced with two vertical biodegradable composite yarns 200V prior to dissolution of biodegradable shells 204 in accordance with one embodiment. FIG. 7 is a cross-sectional view of graft material 102 along the line VII-VII of FIG. 6 upon initial deployment on a vessel wall 702 in accordance with one embodiment.

Referring now of FIGS. 1, 6 and 7 together, stent-graft 100 is deployed within a vessel including the vessel wall 702. For example, stent-graft 100 is deployed to treat an abdominal aortic aneurysm, a thoracic aortic aneurysm, a dissection, or other medical condition.

Upon initial deployment, biodegradable shells 204 remain in their original form and are undissolved. As discussed above, prior to dissolution of biodegradable shells 204, graft material 102 is essentially impermeable.

In FIGS. 6 and 7, a pore 602, e.g., a small space, is illustrated. For example, pore 602 is defined by two adjacent vertical yarns 200V and two adjacent horizontal yarns 200H. The other pores 602 in graft material 102 are defined in a similar manner. Pores 602 are typically formed due to the overlapping nature of yarns 200 and the inability to make yarns 200 completely flush with one another along the entire length of yarns 200. Although a pore 602 is illustrated, in other embodiments, graft material 102 has an absence of pores and is completely impermeable.

Paying particular attention to FIGS. 1 and 7 together, stent-graft 100 contacts vessel wall 702. Accordingly, fluid flows though stent-graft 100, i.e., through lumen 114. Due to the impermeability of stent-graft 100, vessel wall 702 including any defect associated therewith, e.g., a dissection or aneurysm, are excluding from the pressurized fluid flow through stent-graft 100.

FIG. 8 is an enlarged plan view of the section of graft material 102 of FIG. 6 after dissolution of biodegradable shells 204 in accordance with one embodiment. FIG. 9 is a cross-sectional view of graft material 102 along the line IX-IX of FIG. 8 after a period of time after deployment on vessel wall 702 in accordance with one embodiment.

Referring now of FIGS. 1, 8-9 together, after a period of time, biodegradable shells 204 (see FIGS. 6-7) dissolve. However, permanent cores 202 remain in the same configuration as when initially deployed or approximately there so.

Biodegradable shells 204 slowly dissolve from outer surface 210 to inner surface 208 over a period of time. As biodegradable shells 204 dissolve, openings 902 are created between permanent cores 202. Openings 902 increase in size over time as biodegradable shells 204 dissolve.

Over time, biodegradable shells 204 are replaced with tissue 904 from vessel wall 702 that integrates within and through openings 902 as illustrated in FIG. 9. Tissue 904 encases permanent core 202 and fills openings 902 preventing leakage through openings 902 in accordance with this embodiment. The integrate of tissue 904 into graft material 102 provides biological fixation of stent-graft 100 in vessels and prevents endoleaks and migration of stent-graft 100. Generally, stent-graft 100 becomes integrated with the vessel including vessel wall 702.

As discussed below in reference to FIGS. 10-13, stent-graft 100 is used to cover and treat various defects in a vessel.

FIG. 10 is a cross-sectional view of a vessel assembly 1000 including stent-graft 100 of FIG. 1 after initial deployment within a vessel 1002 having a dissection in accordance with one embodiment. FIG. 11 is an enlarged cross-sectional view of a region XI of vessel assembly 1000 of FIG. 10. In FIG. 10, stent-ring 104 is not illustrated for simplicity.

Referring to FIGS. 1, 10-11 together, a dissection is a condition in which an inner layer 1006 of vessel 1002 tears to have a dissection opening 1008. Fluid, e.g., blood, flows through dissection opening 1008 and into a false lumen 1010 between inner layer 1006 and one or more other outer layers 1012 of vessel 1002. Left untreated, false lumen 1010 can rupture outer layers 1012 of vessel 1002 leading to serious complications and often death.

In accordance with this embodiment, stent-graft 100 is deployed to cover and exclude dissection opening 1008. As discussed above, when initially deployed, stent-graft 100 is impermeable thus sealing dissection opening 1008 and preventing pressurized fluid flow through false lumen 1010.

FIG. 12 is a cross-sectional view of region XI of vessel assembly 1000 of FIG. 10 after a period of time after deployment of stent-graft 100 within vessel 1002 in accordance with one embodiment. Referring now to FIGS. 1, 10-12, due to the covering and exclusion of the dissection with stent-graft 100, dissection opening 1008 heals and closes and false lumen 1010 collapses. At the same time, biodegradable shells 204 dissolve allowing tissue 904 integration into openings 902 of stent-graft 100 including between permanent cores 202.

FIG. 13 is a cross-sectional view of a vessel assembly 1302 including a stent-graft 1300 in accordance with one embodiment. Stent-graft 1300 of FIG. 13 is similar to stent-graft 100 of FIG. 1 and only the significant differences are discussed below. Stent-graft 1300 is illustrated with an absence of stent-rings 104 for simplicity but includes stent-rings 104 in other embodiments.

In accordance with this embodiment, a graft material 102A and more generally stent-graft 1300 includes at least three zones 1304, 1306, 1308 in accordance with this embodiment. Proximal seal zone 1304 extends from proximal end 108 to exclusion zone 1306. Exclusion zone 1306 extends from proximal seal zone 1304 to distal seal zone 1308. Distal seal zone 1308 extends from exclusion zone 1306 to distal end 112.

Proximal seal zone 1304 and distal seal zone 1308 include biodegradable composite yarn graft material 102 similar to that discussed. More particularly, only proximal seal zone 1304 and distal seal zone 1308 include biodegradable composite yarns 200 having permanent cores 202 and biodegradable shells 204.

However, exclusion zone 1306 is formed of non-biodegradable material, is permanent, and impermeable. For example, in accordance with various embodiments, exclusion zone 1306 is polyester terephthalate (PET), expanded polyester terephthalate (ePET), or other similar graft material or textile.

Stent-graft 1300 is deployed into a vessel 1310 to exclude an aneurysm 1312 using any one of a number of techniques well known to those of skill in the art. More particularly, proximal seal zone 1304 and distal seal zone 1308 are deployed proximally and distally to aneurysm 1312, respectively.

Proximal seal zone 1304 and distal seal zone 1308 directly contact a vessel wall 1314 of vessel 1310. Over time, biodegradable shells 204 of proximal seal zone 1304 and distal seal zone 1308 dissolve. This allows tissue integration into proximal seal zone 1304 and distal seal zone 1308 of stent-graft 1300 in a manner similar to that discussed above. This, in turn, prevents leakage around proximal seal zone 1304 and distal seal zone 1308 and migration of stent-graft 1300.

Further, exclusion zone 1306 is deployed over aneurysm 1312, i.e., to exclude aneurysm 1312. Accordingly, blood flows through exclusion zone 1306 and more generally through stent-graft 1300 thus excluding aneurysm 1312. As exclusion zone 1306 may not contact vessel wall 1314 but span aneurysm 1312, exclusion zone 1306 does not include biodegradable material such that openings, e.g., see openings 902 of FIGS. 8-9, are not created in stent-graft 1300 in exclusion zone 1306.

It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements. 

What is claimed is:
 1. A prosthesis comprising: a biodegradable composite yarn comprising: a permanent core; and a biodegradable shell.
 2. The prosthesis of claim 1 further comprising: a biodegradable composite yarn graft material comprising the biodegradable composite yarn combined together.
 3. The prosthesis of claim 2 wherein the permanent core and the biodegradable shell are coextruded to form the biodegradable composite yarn.
 4. The prosthesis of claim 1 wherein the permanent core is encased within the biodegradable shell.
 5. The prosthesis of claim 1 wherein the permanent core is permanent when placed in the human body, and the biodegradable shell biodegrades in the human body.
 6. The prosthesis of claim 1 wherein the permanent core is cylindrical and the biodegradable shell is an annular cylinder.
 7. The prosthesis of claim 6 wherein the permanent core and the biodegradable shell are coaxial.
 8. The prosthesis of claim 1 wherein the biodegradable shell has a greater elasticity than the permanent core.
 9. The prosthesis of claim 1 further comprising: a biodegradable composite yarn graft material comprising the biodegradable composite yarn; and at least one stent-ring coupled to the biodegradable composite yarn graft material.
 10. The prosthesis of claim 1 further comprising a graft material comprising a proximal seal zone, an exclusion zone, and a distal seal zone, wherein only the proximal seal zone and the distal seal zone comprises the biodegradable composite yarn.
 11. The prosthesis of claim 1 wherein the exclusion zone consists of a permanent material.
 12. An assembly comprising: a vessel comprising a vessel wall; a prosthesis in contact with the vessel wall, the prosthesis comprising: a permanent core; and a biodegradable shell.
 13. The assembly of claim 12 wherein the prosthesis further comprises a biodegradable composite yarn comprising the permanent core and the biodegradable shell.
 14. The assembly of claim 12 wherein over time the biodegradable shell biodegrades.
 15. The assembly of claim 12 wherein the vessel comprises a dissection, the prosthesis being deployed over a dissection opening of the dissection.
 16. The assembly of claim 12 wherein the vessel comprises an aneurysm, the prosthesis being deployed to exclude the aneurysm.
 17. A method comprising: forming a biodegradable composite yarn comprising a permanent core and a biodegradable shell; and combining the biodegradable composite yarn to form a prosthesis comprising a biodegradable composite graft material.
 18. The method of claim 17 further comprising: deploying the prosthesis within a vessel, wherein upon initial deployment, the biodegradable composite graft material is impermeable to fluid.
 19. The method of claim 18 wherein over time, the biodegradable shell biodegrades creating openings in the biodegradable composite graft material.
 20. The method of claim 19 wherein tissue from the vessel fills the openings and encases the permanent core. 